1. Field of the Invention
The present invention relates to a magnetic recording medium having a non-magnetic primer layer containing a binder and non-magnetic particles, on a flexible non-magnetic support, and having a magnetic layer containing a binder and a ferromagnetic acicular metal powder, thereon. Particularly, it relates to a magnetic recording medium which is excellent in durability and suitable for high density recording.
2. Discussion of Background
In recent years, it has strongly been demanded to adapt magnetic recording media to high density recording with a high frequency. In view of such a demand, a study has been made on a magnetic recording medium employing a thin metal film for the magnetic layer. However, a coating type magnetic recording medium is superior from the viewpoint of the productivity, durability, corrosion resistance, etc., and improvements of a coating type magnetic recording medium have been studied from various aspects. In high frequency recording, problems in the overwriting characteristics and self-demagnetization loss during recording, are substantial, and to avoid such problems, it is necessary to make the magnetic layer thin. However, if the magnetic layer is simply made thin, the durability and the surface property deteriorate. Therefore, a magnetic recording medium of a double layer structure has heretofore been proposed wherein a non-magnetic layer composed mainly of a non-magnetic powder and a binder, is formed beneath the magnetic layer (JP-A-62-154225, JP-A-62-159338). However, with such a double layer structure only, it has been difficult to obtain a magnetic recording medium which is excellent in durability and in electromagnetic conversion characteristics and thus is suitable for high density recording.
JP-A-7-287833 proposes to improve the surface property of the magnetic layer by coating a coating material for a non-magnetic primer layer containing a non-magnetic powder treated with antimony or tin for coating and coating a coating material for a magnetic layer containing a magnetic powder while the coating material for the primer layer is still in a wet state. However, if the upper layer is coated while the lower layer is still in a wet state, the interface will be roughened, and the electromagnetic conversion characteristics tend to deteriorate, when the thickness of the upper layer is thin. Further, the roughening of the interface influences the surface, whereby no satisfactory surface property can be obtained.
It is an object of the present invention to solve such problems and to provide a magnetic recording medium having a magnetic layer and a non-magnetic layer laminated, wherein roughening of the interface between the two layers is little, whereby the electromagnetic conversion characteristics are excellent, and a process for its production.